Apache::RPC::Status(3)User Contributed Perl DocumentatioApache::RPC::Status(3)NAMEApache::RPC::Status - A status monitor similar to Apache::Status for
RPC
SYNOPSIS
# In httpd.conf:
</Location /rpc-status>
SetHandler perl-script
PerlHandler Apache::RPC::Status
</Location>
# In the start-up Perl file:
use Apache::RPC::Status;
DESCRIPTION
The Apache::RPC::Status package is provided as a simple status monitor
for XML-RPC servers running in a mod_perl environment, using the
Apache::RPC::Server class (or derivative of). Patterned after the sta-
tus system provided with mod_perl itself, information is broken down
into a series of screens providing information ranging from the RPC
servers currently configured down to the individual methods provided by
the servers.
Information Screens
There are three basic screens provided by the stock Apache::RPC::Status
package:
Main: Listing of Servers
This screen is the first screen that comes up when the location for
which this class was assigned as a handler is invoked. It lists the
server objects that this running Apache process knows of. Note that
if the servers are defined in such a way as to mean on-demand cre-
ation, then a given child process may not have all the configured
servers in memory. This is by design, it is not a bug. See "Usage
Within <Perl> Sections" in Apache::RPC::Server for details on con-
figuring the RPC servers such that they are pre-loaded into all
child processes.
Server: Details of a Server
Each of the known servers in the main screen links to this screen,
which provides details on the specific server. Information such as
when the server was started (which usually matches the time that
Apache was started), when the specific child was started (which may
not be the same), number of requests servered, and so forth is pro-
vided. Additionally, each of the methods that the server provides
is listed in alphanumeric order, with a link to the next screen.
Method: Details of a Specific Method
For each of the known methods published by a server, this screen
summarizes all that is known about the method itself. The signa-
tures, help text and hidden status (whether the method is visible
to the introspection API that is shipped with RPC::XML::Server) are
all shown. Some optional information is shown if available: if the
method has a version number associated with it, that is displayed.
If the method was loaded from an external XPL file, the file path
and modification-time are also displayed.
The primary purpose of this status system is to allow for checking the
availability and sanity of the RPC servers themselves. For example, if
a server is configured to auto-load methods, and automatically check
for updates, the status system could confirm that a method is available
or is at the correct version.
(Note that auto-loading and auto-updating are done on demand, when a
call is made to the method in question. Thus, the status might not
reflect changes until at least one call has been made. Further, if
there are very many child processes handling the RPC servers, several
calls may be necessary to ensure that the child process answering the
status request also has the most up-to-date impression of the server.)
SUBCLASSING AND EXTENDING
This package is implemented as a method handler for Apache/mod_perl.
This means that is should be relatively easy to subclass this package
to implement an extended version of status reporting, or to provide
handlers for phases of the request lifecycle not otherwise addressed.
Class Methods
There are three class methods defined in this package. One is the con-
structor, the other two are handlers for specific phases in the Apache
request lifecycle.
new(CLASS, ARGS)
This creates a new object of this class and returns a reference to
it. The first argument is the class being created into, the remain-
ing arguments are treated as key/value pairs (note: not a hash ref-
erence). At present, the only additional argument recognized is:
serverclass
This is used when the status monitor is being used with a
server class other than Apache::RPC::Server directly.
Because several methods from that class are invoked, it is
presumed that the class named here is a subclass of
Apache::RPC::Server. If not, the status monitor may not
work correctly, or at all. In the absence of this value,
"Apache::RPC::Server" is assumed. This value may also be
set with the mod_perl PerlSetVar directive. See the docu-
mentation for "init_handler", below.
handler(CLASS, REQUEST)
This is the primary entry-point for the package. This is the han-
dler defined for assignment to "PerlHandler" in a location configu-
ration block. It is invoked by mod_perl as a method handler, thus
the first argument is either the name of the class (in the case of
class-method, or static, invocation) or the object configured as
the handler. The second argument is the Apache request object
itself.
This method derives the query parameters for the request from the
Apache object, and treats them according to the type of information
screen requested:
screen This specifies which screen of the status monitor is to be
displayed. In absence, the value defaults to "main", which
is the internal identifier for the primary screen of the
status monitor system. If the value of this parameter does
not match a known interface hook, then the handler will
signify to mod_perl that it cannot handler the request, by
replying with the "DECLINED" response code.
server When the screen parameter is set to "server", the monitor
displays the server detail screen. In that case, this
parameter specifies which server should be displayed.
Servers are given unique identifiers when they are created,
usually derived from the URL path that they are attached
to. If the value here does not match any known servers, a
warning is sent to the browser.
method When the screen parameter is set to "method", this calls
for the method detail screen. The provided interface hook
to deal with these requests looks for both the server
parameter above and this one, which specifies by name the
method to be laid out in detail. As with the server parame-
ter, if the value in this parameter does not match any
known data, an error is reported to the browser.
Any additional parameters will be preserved by make_url call
detailed below. These are merely the specific ones recognized by
the status monitor as written.
init_handler(CLASS, REQUEST)
This is a very simple handler designed for the PerlChildInitHandler
phase. At present, it only does one simple task (and thus makes no
direct use of either parameter passed to it by mod_perl). However,
it is included mainly as a placeholder for possible future expan-
sion. The current behavior is to check for the existence of direc-
tory-configuration item called "ServerClass", and record the value
if it is set. This is used to specifiy the class from which the RPC
server objects are created, if something other than
Apache::RPC::Server. If this information is passed via the "server-
class" parameter to the new method above, that value overrides any
value here. However, that requires actually creating an object to
use as the handler, whereas this handler may be used directly, as a
static handler. It would be configured outside of any <Location>
blocks, a requirement for the PerlChildInitHandler phase. It is
designed to stack cleanly with any other handlers for that phase,
provided your mod_perl installation supports stacked handlers.
Additional Methods
In addition to the class methods above, the following are provided. In
most cases, these do not rely on any data contained within the actual
object itself. Many may also be called as static methods (these are so
noted). They are provided as a utility, implemented as methods so as to
avoid namespace issues:
version
(May be called as a static method.) Returns the current version of
this module.
apache_status_attach
Attach the Apache::RPC::Status module to the main screen of the
Apache::Status display.
default_object
(May be called as a static method.) Returns a default
Apache::RPC::Status instance when called as a static method.
Returns the calling reference itself, otherwise.
header(REQUEST, TITLE)
Produces the HTML header for a page. Uses the passed-in title
parameter to give the page a title, and extracts any request-spe-
cific information from the Apache request object passed as the
first parameter.
footer(REQUEST)
Produces the HTML footer.
make_url(QUERY|REQUEST, FLAG)
(May be called as a static method.) This creates a URL string for
use as a hyperlink. It makes certain to preserve all parameters in
a CGI-like fashion. Additionally, it can make the URL in such a
fashion as to allow better integration with the Apache::Status
package. If the "FLAG" parameter is passed and is any true value,
then the resulting URL will be tailored for use with Apache::Sta-
tus. The first argument must be either the original request object
as passed by mod_perl, or a reference to a CGI object created from
the request (see CGI for more on the CGI class).
main_screen(REQUEST, QUERY, INTERNAL)
Renders the HTML (minus the header and footer) for the main screen.
The arguments are the Apache request object, a CGI query object
created from the request, and a boolean flag indicating whether the
call into this method was made from within this module or made from
the Apache::Status page.
server_summary(SERVER)
Creates an HTML snippet to provide a summary for the server passed
in as an argument. The passed-in value should be the server object,
not the name.
server_detail(REQUEST, QUERY, INTERNAL)
Renders the HTML (minus header and footer) for a screen describing
a server instance in detail. The server is specified by name in the
query parameters. The arguments are the same as for "main_screen".
method_summary(SERVER, METHOD, BASEURL)
Creates and HTML snippet to provide a summary for the specified
method of the specified server. The third argument is a base-URL to
use for making links to the detailed method page.
method_detail(REQUEST, QUERY, INTERNAL)
Renders the HTML (minus header and footer) for a screen describing
a method on a specific server instance, in detail. The method and
server are specified by name in the query parameters. The arguments
are the same as for "main_screen".
Use and Extension Within Perl Sections
Some extension may be done without necessarily subclassing this pack-
age. The class object are implemented simply as hash references. When a
request is received, the screen parameter (see above) is extracted, and
used to look up in the hash table. If there is a value for that key,
the value is assumed to be a hash reference with at least two keys
(described below). If it does not exist, the handler routine declines
to handle the request. Thus, some degree of extension may be done with-
out the need for developing a new class, if the configuration and
manipulation are done within <Perl> configuration blocks.
Adding a new screen means writing a routine to handle the requests, and
then adding a hook into that routine to the object that is the handler
for the Apache location that serves RPC status requests. The routines
that are written to handle a request should expect four arguments (in
order):
The object reference for the location handler
The Apache request object reference
A query object reference (see below)
A flag that is only passed when called from Apache::Status
The routines are given both the original request object and a query
object reference for sake of ease. The query object is already avail-
able prior to the dispatch, so there is no reason to have each hook
routine write the same few lines to derive a query object from an
Apache request. At the same time, the hooks themselves may need the
Apache object to call methods on. The query object is an instance of
CGI. The flag parameter is passed by the linkage from this status pack-
age to Apache::Status. The primary use for it is to pass to routines
such as make_url that are sensitive to the Apache::Status context.
The return value from these routines must be a reference to a list of
lines of text. It is passed to the print method of the Apache class.
This is necessary for compatibility with the Apache::Status environ-
ment.
To add a new hook, merely assign it to the object directly. The key is
the value of the "screen" parameter defined above, and the value is a
hash reference with two keys:
title
A string that is incorporated into the HTML title for the page.
call
A reference to a subroutine or closure that implements the hook,
and conforms to the conventions described above.
A sample addition:
$stat_obj->{dbi} = {
title => 'RPC-side DBI Pool',
call => \&show_dbi_pool
};
INTEGRATION WITH Apache::Status
This package is designed to integrate with the Apache::Status package
that is a part of mod_perl. However, this is not currently functional.
When this has been debugged, the details will be presented here.
CAVEATS
This is the newest part of the RPC-XML package. While the package as a
whole is now considered beta, this piece may yet undergo some alpha-
like enhancements to the interface and such. However, the design and
planning of this were carefully considered, so any such changes should
be minimal.
LICENSE
This module is licensed under the terms of the Artistic License that
covers Perl. See <http://www.opensource.org/licenses/artis-
tic-license.php> for the license itself.
SEE ALSO
Apache::Status, Apache::RPC::Server, RPC::XML::Method
AUTHOR
Randy J. Ray <rjray@blackperl.com>
perl v5.8.8 2006-02-18 Apache::RPC::Status(3)
